Float type expansion chamber for closed fluid systems



June 29, 1948. A. H. HOFBERG 2,444,351

FLOAT TYPE EXPANSION CHAMBER FOR CLOSED FLUID SYSTEMS Filed May 28, 1943 3maentor Alf H. Hofberg Patented 29,

"UNlTED STATES PATENT OFFICE 2.444.351

FLOAT TYPE EXPANSION CHAMBER FOB CLOSED FLUID SYSTEMS Al! 1!. Hofberg, Medford, N. .L, alllgnor to Radio Corporation of America. a corporation of Dela- Applicatlon Ma! 28, 1943, Serial N0. ("M5 3 Claims. (Cl. 174-12) This invention relates to closed fluid systems and particularly to an improved means for compensating for the expansion and contraction of the fluid in such systems. While the invention will be described as applied to a. closed fluid system for protecting an electrical unit, such as a capacitor, transformer. coil or resistor, it will be understood that the disclosure in this respect is merely illustrative and that the invention is susceptible of various other applications and embodiments.

In stationary electrical installations it is common practice to provide slack-filled containers for those electrical devices which are designed to operate in a liquid medium and to bring the leads for the device out through the bottom of the receptacle so that they will always be covered by the liquid. Such slack-filled electrical devices. however, are unsuited for use on aircraft and other installations where they may be tilted or turned upside down, since in such event the liquid which normally surrounds the leads is replaced by the enclosed air and this lowers the resistance of the device to arc-over in the very region where its resistance should be greatest. In order to obviate this objection, .while at the same time permitting the expansion and contraction of the protecting liquid. it has previously been proposed to make the receptacle in the form of a bellows and to flll it completely with the liquid. The principal objection to this solution of the problem is that such expansible-contractlble receptacles are extremely expensive, their cost frequently being many times that of the electrical devices which they are designed to contain.

Accordingly, the principal object of the present invention is to provide a reliable, yet simple and inexpensive closed fluid system, and one whose successful operation is in no wise impaired by reason of its angular position with respect to the earth.

Other objects and advantages will be apparent and the invention itself will be best understood by a reference to the following specification and to the accompanying drawing wherein: I designates metal sphere. having a weight I on the bottom and containing a single aperture I and a partial is preferably confined to the auxiliary chamber I as by means of an open-work member, such as a screen I. As the liquid in the main and auxiliary chambers expands-more of it is forced into the float C through the aperture 0, where it finds room by compressing the air or other gas therein. Since the float 8 is weighted. the device can be upset or turned over without the air escaping from the float or producing a bubble in the main chamber, which might result in undesired arcing between the leads ll of the electrical device I. Since the only air or other gas in the system is confined to the float 8, it is apparent that the leads II for the unit 2 need not be brought out through the bottom surface of the system, but may be brought out at the sides or at the top, if desired.

The size and initial relative volume of gas and liquid in the float I can easily be determined, for an installation of a given size, by applying the general gas law. In one successful embodiment of the invention wherein the total liquid (a light mineral oil) content was approximately sixty-four cubic inches, 9. weighted metal sphere having a volume of approximately ten and one-half cubic inches was employed. Nearly half of the volume of the sphere was occupied by the fluid at room temperature (27 0.). This arrangement served to compensate, satisfactorily, for the expansion and contraction of the liquid over an interior temperature range of from -50 C. to +90 C.

What is claimed is:

1. In apparatus of the character described, a closed receptacle containing a liquid filling, an electrical unit completely immersed in and protected by said liquid, and a freely-rotatable weighted hollow float having an aperture at the bottom thereof immersed in said liquid and containing a partial filling of a gas to compensate for the expansion and contraction of said fluid in said receptacle.

2. In apparatus of the character described, a receptacle containing a fluid filling. an electrical unit immersed in said fluid and provided with a conductive lead which communicates with the exterior of said receptacle, a hollow weighted float having an aperture at the bottom thereof immersed in and free to rotate within said liquid, said float containing a partial filling of a compressible gas to compensate for the expansion and contraction of said liquid in said receptacle, and means for confining the movement of said float to a region within said receptacle which is remote from said electrical unit and its said conductive lead.

filling l' of the insulating liquid 4. The float 3. The invention as set forth in claim 2 and 3 wherein said hollow float comprises a non-col- Number lapslble sphere. 1,564,656 ALF H. HOFBERG. 2,138,362

REFERENCES CITED 5 The following references are of record in the file of this patent: Number 700,636 UNITED STATES PATENTS 743,765 Number Name Date 10 527386 1,394,143 Coolidge Oct. 18, 1921 Name Date Woodmansee Dec. 8, 1925 Thompson Nov. 29; 1938 FOREIGN PATENTS Country Date Germany Dec. 24, 1940 France Jan. 16, 1933 Germany June 18, 1931 

